kern_physio.c revision 1.88.6.1.2.1
1 /* $NetBSD: kern_physio.c,v 1.88.6.1.2.1 2010/04/21 00:28:16 matt Exp $ */ 2 3 /*- 4 * Copyright (c) 1982, 1986, 1990, 1993 5 * The Regents of the University of California. All rights reserved. 6 * (c) UNIX System Laboratories, Inc. 7 * All or some portions of this file are derived from material licensed 8 * to the University of California by American Telephone and Telegraph 9 * Co. or Unix System Laboratories, Inc. and are reproduced herein with 10 * the permission of UNIX System Laboratories, Inc. 11 * 12 * Redistribution and use in source and binary forms, with or without 13 * modification, are permitted provided that the following conditions 14 * are met: 15 * 1. Redistributions of source code must retain the above copyright 16 * notice, this list of conditions and the following disclaimer. 17 * 2. Redistributions in binary form must reproduce the above copyright 18 * notice, this list of conditions and the following disclaimer in the 19 * documentation and/or other materials provided with the distribution. 20 * 3. Neither the name of the University nor the names of its contributors 21 * may be used to endorse or promote products derived from this software 22 * without specific prior written permission. 23 * 24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34 * SUCH DAMAGE. 35 * 36 * @(#)kern_physio.c 8.1 (Berkeley) 6/10/93 37 */ 38 39 /*- 40 * Copyright (c) 1994 Christopher G. Demetriou 41 * 42 * Redistribution and use in source and binary forms, with or without 43 * modification, are permitted provided that the following conditions 44 * are met: 45 * 1. Redistributions of source code must retain the above copyright 46 * notice, this list of conditions and the following disclaimer. 47 * 2. Redistributions in binary form must reproduce the above copyright 48 * notice, this list of conditions and the following disclaimer in the 49 * documentation and/or other materials provided with the distribution. 50 * 3. All advertising materials mentioning features or use of this software 51 * must display the following acknowledgement: 52 * This product includes software developed by the University of 53 * California, Berkeley and its contributors. 54 * 4. Neither the name of the University nor the names of its contributors 55 * may be used to endorse or promote products derived from this software 56 * without specific prior written permission. 57 * 58 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 59 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 60 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 61 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 62 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 63 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 64 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 65 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 66 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 67 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 68 * SUCH DAMAGE. 69 * 70 * @(#)kern_physio.c 8.1 (Berkeley) 6/10/93 71 */ 72 73 #include <sys/cdefs.h> 74 __KERNEL_RCSID(0, "$NetBSD: kern_physio.c,v 1.88.6.1.2.1 2010/04/21 00:28:16 matt Exp $"); 75 76 #include <sys/param.h> 77 #include <sys/systm.h> 78 #include <sys/buf.h> 79 #include <sys/proc.h> 80 #include <sys/once.h> 81 #include <sys/workqueue.h> 82 #include <sys/kmem.h> 83 84 #include <uvm/uvm_extern.h> 85 86 ONCE_DECL(physio_initialized); 87 struct workqueue *physio_workqueue; 88 89 /* 90 * The routines implemented in this file are described in: 91 * Leffler, et al.: The Design and Implementation of the 4.3BSD 92 * UNIX Operating System (Addison Welley, 1989) 93 * on pages 231-233. 94 */ 95 96 /* #define PHYSIO_DEBUG */ 97 #if defined(PHYSIO_DEBUG) 98 #define DPRINTF(a) printf a 99 #else /* defined(PHYSIO_DEBUG) */ 100 #define DPRINTF(a) /* nothing */ 101 #endif /* defined(PHYSIO_DEBUG) */ 102 103 struct physio_stat { 104 int ps_running; 105 int ps_error; 106 int ps_failed; 107 off_t ps_endoffset; 108 buf_t *ps_orig_bp; 109 kmutex_t ps_lock; 110 kcondvar_t ps_cv; 111 }; 112 113 static void 114 physio_done(struct work *wk, void *dummy) 115 { 116 struct buf *bp = (void *)wk; 117 size_t todo = bp->b_bufsize; 118 size_t done = bp->b_bcount - bp->b_resid; 119 struct physio_stat *ps = bp->b_private; 120 bool is_iobuf; 121 122 KASSERT(&bp->b_work == wk); 123 KASSERT(bp->b_bcount <= todo); 124 KASSERT(bp->b_resid <= bp->b_bcount); 125 KASSERT((bp->b_flags & B_PHYS) != 0); 126 KASSERT(dummy == NULL); 127 128 vunmapbuf(bp, todo); 129 uvm_vsunlock(bp->b_proc->p_vmspace, bp->b_data, todo); 130 131 mutex_enter(&ps->ps_lock); 132 is_iobuf = (bp != ps->ps_orig_bp); 133 if (__predict_false(done != todo)) { 134 off_t endoffset = dbtob(bp->b_blkno) + done; 135 136 /* 137 * we got an error or hit EOM. 138 * 139 * we only care about the first one. 140 * ie. the one at the lowest offset. 141 */ 142 143 KASSERT(ps->ps_endoffset != endoffset); 144 DPRINTF(("%s: error=%d at %" PRIu64 " - %" PRIu64 145 ", blkno=%" PRIu64 ", bcount=%d, flags=0x%x\n", 146 __func__, bp->b_error, dbtob(bp->b_blkno), endoffset, 147 bp->b_blkno, bp->b_bcount, bp->b_flags)); 148 149 if (ps->ps_endoffset == -1 || endoffset < ps->ps_endoffset) { 150 DPRINTF(("%s: ps=%p, error %d -> %d, endoff %" PRIu64 151 " -> %" PRIu64 "\n", 152 __func__, ps, 153 ps->ps_error, bp->b_error, 154 ps->ps_endoffset, endoffset)); 155 156 ps->ps_endoffset = endoffset; 157 ps->ps_error = bp->b_error; 158 } 159 ps->ps_failed++; 160 } else { 161 KASSERT(bp->b_error == 0); 162 } 163 164 ps->ps_running--; 165 cv_signal(&ps->ps_cv); 166 mutex_exit(&ps->ps_lock); 167 168 if (is_iobuf) 169 putiobuf(bp); 170 } 171 172 static void 173 physio_biodone(struct buf *bp) 174 { 175 #if defined(DIAGNOSTIC) 176 struct physio_stat *ps = bp->b_private; 177 size_t todo = bp->b_bufsize; 178 179 KASSERT(ps->ps_running > 0); 180 KASSERT(bp->b_bcount <= todo); 181 KASSERT(bp->b_resid <= bp->b_bcount); 182 #endif /* defined(DIAGNOSTIC) */ 183 184 workqueue_enqueue(physio_workqueue, &bp->b_work, NULL); 185 } 186 187 static void 188 physio_wait(struct physio_stat *ps, int n) 189 { 190 191 KASSERT(mutex_owned(&ps->ps_lock)); 192 193 while (ps->ps_running > n) 194 cv_wait(&ps->ps_cv, &ps->ps_lock); 195 } 196 197 static int 198 physio_init(void) 199 { 200 int error; 201 202 KASSERT(physio_workqueue == NULL); 203 204 error = workqueue_create(&physio_workqueue, "physiod", 205 physio_done, NULL, PRI_BIO, IPL_BIO, WQ_MPSAFE); 206 207 return error; 208 } 209 210 #define PHYSIO_CONCURRENCY 16 /* XXX tune */ 211 212 /* 213 * Do "physical I/O" on behalf of a user. "Physical I/O" is I/O directly 214 * from the raw device to user buffers, and bypasses the buffer cache. 215 * 216 * Comments in brackets are from Leffler, et al.'s pseudo-code implementation. 217 */ 218 int 219 physio(void (*strategy)(struct buf *), struct buf *obp, dev_t dev, int flags, 220 void (*min_phys)(struct buf *), struct uio *uio) 221 { 222 struct iovec *iovp; 223 struct lwp *l = curlwp; 224 struct proc *p = l->l_proc; 225 int i, error; 226 struct buf *bp = NULL; 227 struct physio_stat *ps; 228 int concurrency = PHYSIO_CONCURRENCY - 1; 229 230 error = RUN_ONCE(&physio_initialized, physio_init); 231 if (__predict_false(error != 0)) { 232 return error; 233 } 234 235 DPRINTF(("%s: called: off=%" PRIu64 ", resid=%zu\n", 236 __func__, uio->uio_offset, uio->uio_resid)); 237 238 flags &= B_READ | B_WRITE; 239 240 if ((ps = kmem_zalloc(sizeof(*ps), KM_SLEEP)) == NULL) 241 return ENOMEM; 242 /* ps->ps_running = 0; */ 243 /* ps->ps_error = 0; */ 244 /* ps->ps_failed = 0; */ 245 ps->ps_orig_bp = obp; 246 ps->ps_endoffset = -1; 247 mutex_init(&ps->ps_lock, MUTEX_DEFAULT, IPL_NONE); 248 cv_init(&ps->ps_cv, "physio"); 249 250 /* Make sure we have a buffer, creating one if necessary. */ 251 if (obp != NULL) { 252 /* [raise the processor priority level to splbio;] */ 253 mutex_enter(&bufcache_lock); 254 /* Mark it busy, so nobody else will use it. */ 255 while (bbusy(obp, false, 0, NULL) == EPASSTHROUGH) 256 ; 257 mutex_exit(&bufcache_lock); 258 concurrency = 0; /* see "XXXkludge" comment below */ 259 } 260 261 uvm_lwp_hold(l); 262 263 for (i = 0; i < uio->uio_iovcnt; i++) { 264 bool sync = true; 265 266 iovp = &uio->uio_iov[i]; 267 while (iovp->iov_len > 0) { 268 size_t todo; 269 vaddr_t endp; 270 271 mutex_enter(&ps->ps_lock); 272 if (ps->ps_failed != 0) { 273 goto done_locked; 274 } 275 physio_wait(ps, sync ? 0 : concurrency); 276 mutex_exit(&ps->ps_lock); 277 if (obp != NULL) { 278 /* 279 * XXXkludge 280 * some drivers use "obp" as an identifier. 281 */ 282 bp = obp; 283 } else { 284 bp = getiobuf(NULL, true); 285 bp->b_cflags = BC_BUSY; 286 } 287 bp->b_dev = dev; 288 bp->b_proc = p; 289 bp->b_private = ps; 290 291 /* 292 * [mark the buffer busy for physical I/O] 293 * (i.e. set B_PHYS (because it's an I/O to user 294 * memory, and B_RAW, because B_RAW is to be 295 * "Set by physio for raw transfers.", in addition 296 * to the "busy" and read/write flag.) 297 */ 298 bp->b_oflags = 0; 299 bp->b_cflags = BC_BUSY; 300 bp->b_flags = flags | B_PHYS | B_RAW; 301 bp->b_iodone = physio_biodone; 302 303 /* [set up the buffer for a maximum-sized transfer] */ 304 bp->b_blkno = btodb(uio->uio_offset); 305 if (dbtob(bp->b_blkno) != uio->uio_offset) { 306 error = EINVAL; 307 goto done; 308 } 309 bp->b_bcount = MIN(MAXPHYS, iovp->iov_len); 310 bp->b_data = iovp->iov_base; 311 312 /* 313 * [call minphys to bound the transfer size] 314 * and remember the amount of data to transfer, 315 * for later comparison. 316 */ 317 (*min_phys)(bp); 318 todo = bp->b_bufsize = bp->b_bcount; 319 #if defined(DIAGNOSTIC) 320 if (todo > MAXPHYS) 321 panic("todo(%zu) > MAXPHYS; minphys broken", 322 todo); 323 #endif /* defined(DIAGNOSTIC) */ 324 325 sync = false; 326 endp = (vaddr_t)bp->b_data + todo; 327 if (trunc_page(endp) != endp) { 328 /* 329 * following requests can overlap. 330 * note that uvm_vslock does round_page. 331 */ 332 sync = true; 333 } 334 335 /* 336 * [lock the part of the user address space involved 337 * in the transfer] 338 * Beware vmapbuf(); it clobbers b_data and 339 * saves it in b_saveaddr. However, vunmapbuf() 340 * restores it. 341 */ 342 error = uvm_vslock(p->p_vmspace, bp->b_data, todo, 343 (flags & B_READ) ? VM_PROT_WRITE : VM_PROT_READ); 344 if (error) { 345 goto done; 346 } 347 vmapbuf(bp, todo); 348 349 BIO_SETPRIO(bp, BPRIO_TIMECRITICAL); 350 351 mutex_enter(&ps->ps_lock); 352 ps->ps_running++; 353 mutex_exit(&ps->ps_lock); 354 355 /* [call strategy to start the transfer] */ 356 (*strategy)(bp); 357 bp = NULL; 358 359 iovp->iov_len -= todo; 360 iovp->iov_base = (char *)iovp->iov_base + todo; 361 uio->uio_offset += todo; 362 uio->uio_resid -= todo; 363 } 364 } 365 366 done: 367 mutex_enter(&ps->ps_lock); 368 done_locked: 369 physio_wait(ps, 0); 370 mutex_exit(&ps->ps_lock); 371 372 if (ps->ps_failed != 0) { 373 off_t delta; 374 375 delta = uio->uio_offset - ps->ps_endoffset; 376 KASSERT(delta > 0); 377 uio->uio_resid += delta; 378 /* uio->uio_offset = ps->ps_endoffset; */ 379 } else { 380 KASSERT(ps->ps_endoffset == -1); 381 } 382 if (bp != NULL && bp != obp) { 383 putiobuf(bp); 384 } 385 if (error == 0) { 386 error = ps->ps_error; 387 } 388 mutex_destroy(&ps->ps_lock); 389 cv_destroy(&ps->ps_cv); 390 kmem_free(ps, sizeof(*ps)); 391 392 /* 393 * [clean up the state of the buffer] 394 * Remember if somebody wants it, so we can wake them up below. 395 * Also, if we had to steal it, give it back. 396 */ 397 if (obp != NULL) { 398 KASSERT((obp->b_cflags & BC_BUSY) != 0); 399 400 /* 401 * [if another process is waiting for the raw I/O buffer, 402 * wake up processes waiting to do physical I/O; 403 */ 404 mutex_enter(&bufcache_lock); 405 obp->b_cflags &= ~(BC_BUSY | BC_WANTED); 406 obp->b_flags &= ~(B_PHYS | B_RAW); 407 obp->b_iodone = NULL; 408 cv_broadcast(&obp->b_busy); 409 mutex_exit(&bufcache_lock); 410 } 411 uvm_lwp_rele(l); 412 413 DPRINTF(("%s: done: off=%" PRIu64 ", resid=%zu\n", 414 __func__, uio->uio_offset, uio->uio_resid)); 415 416 return error; 417 } 418 419 /* 420 * Leffler, et al., says on p. 231: 421 * "The minphys() routine is called by physio() to adjust the 422 * size of each I/O transfer before the latter is passed to 423 * the strategy routine..." 424 * 425 * so, just adjust the buffer's count accounting to MAXPHYS here, 426 * and return the new count; 427 */ 428 void 429 minphys(struct buf *bp) 430 { 431 432 if (bp->b_bcount > MAXPHYS) 433 bp->b_bcount = MAXPHYS; 434 } 435
Indexes created Mon Sep 29 21:09:56 GMT 2025